The present invention relates, in general, to measurement systems and, more particularly, to the measurement systems for electrical signals.
Electronic devices (also referred to herein as modules) typically include a relatively small number of terminals and each terminal is typically dedicated to a specific purpose. For example, certain electronic modules have only a terminal dedicated for providing power to the module, a terminal dedicated for providing ground, and a terminal dedicated for providing output data. No terminal is provided for inputting data to such modules. A small number of dedicated terminals minimizes overall module size and simplifies the interface. Therefore, adding a new terminal for an additional purpose is undesirable, particularly if the additional purpose is not needed during mission mode operations. Including a terminal that is useful only during a configuration mode operation is undesirable for a variety of reasons. For example, an additional terminal consumes valuable space and materials and increases interface complexity, which in turn increases the risk of confusion as to which terminal is which.
Programming an electronic sensor module with sensor calibration data is one example of a function for which an additional terminal might be needed during only a limited portion of a module's lifetime. Electronic sensor modules and other similar electronic devices typically require some form of calibration of their output to compensate for incidental design variations that occur during manufacturing or other changes that occur during operational use. Electrical calibration is performed, for example, by first manufacturing the sensor module, stimulating the completed sensor module with a known stimulus, comparing the module's output with an expected output corresponding to the known stimulus, and recording in a memory a table of calibration data that is thereafter referenced by the sensor module when outputting sensor readings. Consequently, the sensor module is able to compensate for any variations detected with respect to the expected output corresponding to the known stimulus. After the electronic sensor module is calibrated and performing its sensing function, additional data input is rarely, if ever, required. Therefore, use of a dedicated terminal for entering calibration data is undesirable because the dedicated terminal would have little use relative to other terminals while consuming valuable space and materials and increasing interface complexity.
A variety of techniques exist for loading calibration data into an electronic sensor module or other electronic module without using a dedicated terminal. However, certain existing techniques require integration of overdriving circuitry into the electronic module, which consumes a large area and large amounts of power. Moreover, many existing techniques preclude or prevent any data from being output by the electronic module while calibration data is loaded.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference characters in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or an anode of a diode, and a control electrode means an element of the device that controls current flow through the device such as a gate of an MOS transistor or a base of a bipolar transistor. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action and the initial action. The use of the words approximately, about, or substantially means that a value of an element has a parameter that is expected to be very close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to about ten percent (10%) (and up to twenty percent (20%) for semiconductor doping concentrations) are regarded as reasonable variances from the ideal goal of exactly as described.